COMMENT:
Asita was, with his whole being, devoted to sitting. And so through Asita the king was able to observe, perceive, hear and learn something that was a word, an instruction, a direction, and/or an order, which caused the king to have a spring in his step.

That direction which put a spring in the king's step, I venture to suggest, was a lengthening and widening direction. As an order, it might be expressed “Let the head go forward and up in such a way that the spine lengthens and the back widens!” If vacanam is understood to mean “a word,” the word might be up.

Compare EHJ's “When the king heard him speak thus, his bearing was disordered with delight,”

EHJ's translation has the virtue, as always, of his effort to mirror Aśvaghoṣa's original Sanskrit as closely as he can. But on this occasion the spirit of the original, as I read it, is better captured by the Chinese translation. The king's bearing was not disordered; on the contrary, thanks to Asita, the king's whole being was informed and ordered by a direction that freed him from all disordered mental states like intellectual doubt.